Some high traffic web sites serve millions of page views a minute. A single page view request may result in many calls to downstream services that span multiple backend tiers. Though web applications depend on downstream services, application developers typically have no insight on the relationships and performance of those services. This lack of insight poses a number of major challenges, such as performance optimization and root cause analysis.
The approaches described in this section are approaches that could be pursued, but not necessarily approaches that have been previously conceived or pursued. Therefore, unless otherwise indicated, it should not be assumed that any of the approaches described in this section qualify as prior art merely by virtue of their inclusion in this section.